OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-2) - 3*a(n-4) -a(n-6) for n>7.
Empirical g.f.: 2*x*(2 + 3*x - 4*x^3 - 5*x^4 - x^5 - x^6) / (1 - 4*x^2 + 3*x^4 + x^6). - Colin Barker, Oct 27 2018
EXAMPLE
Some solutions for n=3:
..1..2..1....1..2..1....2..1..1....2..1..2....1..2..2....2..1..2....2..1..1
..2..0..0....2..0..0....1..0..0....1..0..0....2..0..0....1..0..0....1..0..0
..2..1..2....1..0..0....1..0..0....2..0..0....2..0..0....1..0..0....2..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 31 2014
STATUS
approved